h1,
input,
button {
  margin: 0;
  padding: 0;
}

.box {
  width: 500px;
  margin: 0 auto;
}
.form {
  width: 500px;
  margin-bottom: 10px;
}
.form > span {
  width: 70px;
  border: 1px solid skyblue;
  font-size: 18px;
  line-height: 1;
}
.form > input {
  outline: none;
  width: 400px;
  height: 20px;
}

/* 隐藏选项+遮盖层 */
.hidden-box {
  width: 500px;
  height: 500px;
  display: none;
  background-color: white;
  position: absolute;
  z-index: 50;
  top: 100px;
}
.cover {
    position: fixed;
    top: 0;
    left: 0;
    bottom: 0;
    right: 0;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.4);
    display: none;
}
